THE INTROBA IMPACT FUND: OUR COMMITMENT TO THINKING AHEAD
The Impact Fund specifically supports thought leadership and transformational initiatives around sustainability and digital innovation and encourages collaboration with external partners. This initiative aims to share our findings and insights with the AEC industry as a whole to create collective knowledge and stimulate action that has a positive impact on the built environment.
Learn more about the Impact Fund
Acknowledgments
This study is a direct response to the World Green Building Council’s 2021 Beyond Buildings report1, calling for the architecture, engineering, and construction (AEC) industry to approach buildings and infrastructure in a more integrated manner to stay within the 1.5 degrees Celsius threshold for global warming. There has been progress, but it has been slow. Our hope is that this report acts as a catalyst to unlock higher impact policies and refocus private resources.
This report has also been inspired by the thoughts of Lloyd Alter, Steven Biersteker, Uytae Lee, Kelly Alvarez Doran, Helen Lui, Kjell Anderson, and Justin Schwartzhoff. My thanks to each of you for sharing your ideas on sustainability and urbanism in public forums.
I would also like to thank Introba for sponsoring this research through its Impact Fund. The chance to consider how we perceive and shape our built environments outside the boundaries of a conventional project is a privilege.
Additionally, TYLin provided key validation for our road works service life assumptions and supplied the methodology and data used to assess emissions from User Transportation, a significant portion of total emissions. Perkins&Will also granted access to internal studies on embodied carbon in interiors, supporting the validation of sources cited in the report.
Finally, I’d like to thank each of the people listed below who contributed key ideas and assumptions underpinning the report:
Introba: Ezgi Yuruk, Riya Tolia, Kevin Welsh, Emily Codlin, Louise Hamot, Richard Palmer, Miguel Lopez, Zeina Krayim, Mat Loup, Tracy Wong, and Patrick Matheson.
TYLin Kate Sargent and Melvin Wah, Ryan Abbotts, Matt Palzkill, and Grant Taylor.
Life cycle assessment (LCA) and energy models are fantastic tools used to influence key building design decisions. However, these models almost never look up far enough to consider their surroundings.
Built environments are created by distinct combinations of buildings and infrastructure, and yet our decarbonization solutions often focus on one and fail to consider the other as part of a living system.
Architecture 2030 estimates that transportation and the built environment combined are responsible for about two-thirds of global emissions 2 . If these emissions could be tackled and reduced holistically, the ambitions of the 2015 Paris Agreement to limit global warming to 1.5 degrees Celsius 3 may move closer to reality.
After months of research, the Introba and TYLin City Solutions 4 teams have identified how to connect the dots between carbon emissions accounting methods for buildings, urban infrastructure, and transportation. We can now enable our clients to begin to quantify the whole life carbon emissions 5 of entire built environments. And we are sharing our results to spur industry partners onwards.
To discover the most effective actions that must be taken at scale to decarbonize new construction around the world, we looked at the hypothetical carbon story for net-zero versions of two globally recognized forms of built environment that could house 600 people:
• A tall, urban tower
• A suburban community
We selected these two settings because they are regularly criticized as unsustainable, and they are familiar to many as the backdrops of American TV shows and movies. This also influenced us to primarily draw on North American sources for key details like the size of a typical home and annual daily travel patterns.
We found:
• Current definitions of Zero Emissions buildings won’t create Zero Emissions built environments: for both Urban and Suburban forms, total lifetime carbon emissions are projected to exceed 44 million kilograms of carbon (>1900 kgCO2e per m2 of floor area) - even if newly-built homes align with Part 1 of the USA’s “National Definition of a Zero Emissions Building6”.
• In both the Urban and Suburban forms, 55-60% of emissions released before 2030 will be from the upfront embodied carbon of the materials needed to build our structures and enclosures.
• Only a few years after that, we project cumulative user transportation impacts will overtake the upfront burst of embodied impacts. By 2084, user transportation will account for 66% (nearly two-thirds) of total lifetime carbon emissions.
• Suburban settings appear to be the higher emissions form of built environmentbut only slightly (just over 15%). This is primarily driven (pun intended?) by longer travel distances and user preferences in transportation mode.
What does this mean?
• Governments and the AEC industry must deprioritize the expansion of automobile-centric infrastructure — most critically, parking — even in light of vehicle electrication trends, and redirect that funding and design effort into incentivising shared, sustainable transportation measures and procuring lower embodied carbon materials.
• Organizations that deploy capital for urban development purposes must analyze carbon at the scale of the built environment to identify their lowest carbon financing opportunities.
As part of our role in building design teams, we quantify the carbon emissions of our building projects. We typically use energy modelling for operational carbon emissions and increasingly use LCA modelling for embodied carbon emissions.
Although these are fantastic tools that influence key emissions-related design decisions, these models almost never consider a project’s spatial context. This means these models fail to consider a building’s place within its built environment.
No matter where you live on our planet, you likely realize buildings do not exist as islands. Buildings are linked by civil infrastructure such as drinking water pipes, telecommunications wires, power cables, sidewalks, roads, and more. The built environments in which we live are created by distinct combinations of buildings and infrastructure, which have a great influence on our daily lives.
transportation options such as EV chargers, cyclist change rooms, carsharing, bike racks, and choosing transit-oriented sites through our sustainability consulting services. However, quantifying emissions from future resident transportation within those frameworks has proved elusive.
Our partners at TYLin City Solutions spend a lot of time thinking about the way people move and how we can plan for a transportation future that adapts to the evolving needs of communities and the climate. They have been at the forefront, working with clients to overcome persistent transportation challenges and implement their desired sustainable transportation futures.
The methods historically available to governments and the AEC industry have struggled to holistically measure carbon from buildings. In many jurisdictions, the anticipated kilograms of carbon dioxide (kgCO2) emitted by a building are not addressed explicitly. Instead, most jurisdictions focus on kilowatts or dollars. Even where carbon-focused targets exist, these are usually divided by topic: setting limits for operational carbon, refrigerant leakage, and/or embodied carbon in isolation.
“We
shape our buildings; thereafter they shape us.”
Winston Churchill, House of Lords, 1943
One of the most important aspects they influence is our daily transportation choices, which are a major source of carbon emissions at the city and regional scale.
Architecture 2030 estimates that together, transportation and the built environment are responsible for about 64% of global carbon emissions. If those emissions can be addressed, the impact could be monumental.
We have long advocated for including building design elements that promote sustainable
What does this mean?
After months of research, Introba and TYLin City Solutions have identified how to connect the dots between carbon emissions accounting methods for buildings, urban infrastructure, and transportation. This means we can enable our clients and partners to begin to quantify the whole-life carbon emissions of entire built environments.
Why is this important?
In simple terms: What gets measured gets managed.
This effectively puts blinders on design and construction teams. As a result, all-too-limited resources get allocated to achieving kilowatt or energy-cost targets, even when higher-impact and lower-cost carbon savings measures may be available and known. There are almost certainly even higher impact strategies that are familiar to architects and planners and require no new technology. However, we as engineering professionals have not been able to account for them in the right units historically and so have not recognized their true value.
This study aims to overcome this knowledge barrier by identifying the answers to our core questions, so that financiers, planners, developers, and designers can enact at scale the highest-impact strategies.
Since humanity is rapidly running out of time to limit global warming to 1.5°C, we cannot afford to make any more suboptimal decisions about these emissions. Any carbon reductions achieved today buy society more time to reach net zero emissions overall.
Our Two Built Environment Models
Conventional wisdom holds that six-story midrise buildings are the most ideal form of climate-friendly development. Therefore, this study examined two forms of built environment commonly critiqued by the emissions-focused design community: tall, urban, concrete towers and sprawling, suburban communities.
Tall, Urban Tower 1
Tall concrete towers have been greatly criticized for their high emissions; even if designed as Passive Houses (which have much lower operational emissions) and in close proximity to transit, they use gargantuan quantities of concrete, metal, and glass. 11 12 13
We kept two key dates in mind for this exercise:
Suburban Community
When greenhouse gas emissions need to be cut by roughly 50% to keep global warming below 1.5°C, as per the Paris Agreement.
To capture a 60-year lifespan, aligning with leading standards such as the RICS WLCA-BE V2 standard7 in the UK, the Canadian National Guidelines for Whole-Building Life Cycle Assessment8 , LEED 9, and the Australian Green Star standard10
Sprawling, suburban communities, on the other hand, are rarely seen as sustainable due to their reliance on private automobiles and the vast tracts of natural spaces converted to paved areas, even though the buildings are frequently made from light wood frames and can have significant amounts of private green space around them.
These judgments only consider part of the picture. Just as most people recognize that it is an unfair comparison to claim a Tesla Model 3 is lower carbon than a Toyota Camry based on tailpipe emissions alone — you must also consider the upstream electricity emissions and the emissions needed to manufacture and dispose of the batteries or engine block — we must consider the whole picture for our built environment.
“We were originally just going to model real cities, but we quickly realized there were way too many parking lots in the real world.”
Stone Librande, Lead Designer for SimCity (the video game)14
Approach
Inspired by the 2023 RICS Whole Life Carbon framework v215 , which mentions “user carbon” as LCA Module B8 in addition to operational emissions falling within LCA Stage B6, with the remaining embodied emissions being split up into into Modules A1-C4, Introba led an indicative study of two common built environments seen in North America. The graphic on the right illustrates the lifecycle of a built asset.
15 The Royal Institution of Chartered Surveyors Whole Life Carbon framework v2 expands on the more commonly referenced EN (15978 + 21930) and ISO (14044 + 14040) standards, which define the lifecycle stages of a building. It was co-authored by Introba, and can be accessed here.
16 LULUCF stands for “Land Use, Land Use Change, and Forestry”, a term used by the IPCC for Land-based GHG emissions and removals from human activities, in this case primarily from land converted from nature to cities.
17 Refrigerant Leakage is not consistently defined as an “Operational” or “Embodied” emission by the leading standards mentioned throughout this report. For the sake of simple communication, we have listed it as an “Operational” emission as most emissions occur during the ‘in use’ phase.
To make this study as comprehensive as possible, we accounted for the following elements:
• Embodied Impacts from the materials needed for:
o Structures and enclosures
o Interiors (finishes and furnishings)
o Mechanical, electrical, and plumbing systems
o Civil infrastructure
o Live planting and other landscaping impacts
o Land use, land use change, and forestry (LULUCF)16
• Operational Impacts from
o Operational energy
o Refrigerant Leakage17
• User Transportation Impacts
Approach
Identifying our Two Communities
Urban Tower 1
Tall,
To complete the study, we first identified a project that Introba had worked on recently that matched a few key criteria:
✓ Residential-only usage
✓ Unquestionably “Tall” and “Urban”
✓ Sufficiently advanced architectural design
✓ Recently completed project-specific LCA and energy models
In order to develop a reasonably comparable “Suburban Community” we then identified the number of people that would reasonably be expected to live in the “Urban Tower”, based on the number of bedrooms per unit, using a “N+1” formula. This assumed that one person would live in a studio apartment, two people in a one-bedroom apartment, and so on.
With an estimated 600 people living in the Urban Tower, we set about identifying the suburban form that would be home to an equal number of people.
Suburban Community 2
To do this, we conducted a review of seven separate suburban developments that were being actively marketed in 2023 by three separate development companies to identify the median suburban home. The key criteria for this exercise were:
✓ Residential-only usage
✓ Unquestionably “Wide” and “Suburban”
✓ Had publicly available architectural floorplans, renderings, statistics, and community plans
The home selected was a three-bedroom, 1,830-square-foot (170m2), two-story home with a single-car garage, to aligned with the media’s impressions of a typical “American Dream” middle-class home. This home is being offered for sale as part of a large master-planned community that will provide housing for far more than 600 people. Therefore, we had to identify how much of that community would be needed for only 600 people, including not only the land allocated for each home, driveway, and yard, but also for roads, sidewalks, and stormwater management ponds.
Approach
Estimating Emissions
Having selected our two archetypes for the two forms of built environment, we now had to estimate our carbon emissions.
A core assumption of this study and our starting place is that we are dealing with effectively operationally decarbonized buildings . This aligns with the goals of the Architecture 2030 Challenge, leading state/provincial ambitions18 , and the World Green Building Council’s call for all new buildings to be net zero operational carbon (via the Advancing Net Zero calls19).
MEP Systems and Refrigerants
This effectively means that we are counting on our projects using heat-pump based HVAC systems with energy coming from either onsite renewables and/or clean grids 20 .
To estimate the embodied impacts of the materials needed for ductwork, piping and other elements of heating, ventilation, and air conditioning (HVAC) systems, we started by using data from the Chartered Institution of Building Services Engineers (CIBSE) TM65.1 study 21. Then, using internally-conducted studies 22 led by our UK office that also utilized the CIBSE TM65 methodology (ensuring consistency), we expanded our lens from just HVAC to the full suite for mechanical, electrical, plumbing (MEP) and Fire Suppression system elements.
While we assumed that the HVAC systems in those buildings will use conventional refrigerants (R410a), we have also assumed that is only true for the first HVAC system installed. We assumed future systems to be either R744 (Refrigerantgrade CO2) or R32-based systems that align with the intent of the Kigali Amendment 23 to the Montreal Protocol24
This has a drastic impact on anticipated impacts from refrigerant leakage. The quantities and types of refrigerant per system were based on real products from manufacturer cutsheets, with sizes based on anticipated heating and cooling demand. Our Global Warming Potentials25 values for these refrigerants came from the Intergovernmental Panel on Climate Change’s (IPCC) AR4 report 26, and we used leakage rate assumptions consistent with those within LEED v4’s Enhanced Refrigerants credit 27 .
18 Such as the BC Zero Carbon Step Code https://energystepcode.ca/zero-carbon/
19 https://worldgbc.org/advancing-net-zero
Structure and Enclosure
To estimate the impacts from the structure and enclosure, we used data from our own LCA model for the urban case and used the weighted average Material Carbon Intensity from the Emissions of Materials Benchmark Assessment for Residential Construction (EMBARC) study28 to identify the A1-A3 emissions intensity of the typical suburban case. We then scaled those numbers across the full life cycle using the approach listed within the City of Vancouver’s Embodied Carbon Modelling Guidelines 29
Finishes and Fixtures, Furniture, and Equipment
To estimate the impacts from finishes and fixtures, furniture, and equipment (FF&E), we looked at the 6 Camden Mews study30 by the British firm Max Fordham to identify a reasonable emissions intensity for each LCA stage, and then scaled that based on the floor areas of the urban and suburban scenarios.
20 This is a challenging goal in some regions, but in others it is becoming commonplace. For example, in Vancouver, Canada, Introba is involved in apartments under construction (https://viennahouse.ca/ ) that we project will emit 41 times less operational carbon annually than a similar building from 15 years ago.
21 Study authored by Introba https://www.cibse.org/knowledge-research/knowledge-portal/tm65-1-embodied-carbon-in-building-services-residential-heating
23 The Kigali Amendment focused on reducing the use of hydrofluorocarbons (HFCs), gases frequently used as refrigerants in HVAC systems. While HFCs are harmless to the ozone layer, they are potent greenhouse gases with GWPs thousands of times higher than carbon dioxide (CO ).
24 To learn more, read the Introba-authored Refrigerants & Environmental Impacts: A Best Practice Guide: https://www.introba.com/news/refrigerants-environmental-impacts-best-practice-guide
25 All greenhouse gases have varying lifetimes and atmospheric heat-trapping abilities. To overcome this, the Intergovernmental Panel on Climate Change (IPCC) publishes each greenhouse gas’s ability to trap heat in the atmosphere compared to carbon dioxide – aka its “GWP”. This means CO₂ is the “Reference Unit”, which is also why it has become more common in industry circles to refer to “Carbon Dioxide Equivalent” or just carbon instead of GHGs. As we have done throughout this study.
To estimate excavation emissions, we used values from OneClickLCA multiplied by the volume of the below-grade area for the urban scenario.
To estimate civil infrastructure impacts, we used data from our own LCA model for a past infrastructure project to estimate the thickness, widths, and materiality of roads and sidewalks, and multiplied those by the anticipated areas of road and sidewalk needed for 150 homes in the suburban scenario based on the masterplan layout of the selected home archetype.
We refined key assumptions on typical road service life thanks to feedback from the TYLin team. No infrastructure impacts were assigned to the urban model as we assumed it was happening within an infill setting, meaning no substantial areas of new roads or sidewalks would be needed.
Landscaping
New sidewalks along at least one face of the property line would likely be necessary for the urban model. We accounted for this within the landscape emissions (as a part of the “hardscape”.) Landscape planting has also been accounted for in both scenarios, using values from the Climate Positive Design Pathfinder tool31
To estimate Land Use, Land Use Change, and Forestry emissions for land conversions from agricultural/natural to settlement, we looked at Canada’s latest submission to the UN Framework Convention on Climate Change32. The impacts of this category on the overall result were sufficiently minor that we felt comfortable including them even though it is an incredibly complex topic.
User Transportation
ESTIMATING DAILY TRAVEL PATTERNS:
Vehicle Miles Traveled (VMT) is the key metric we used as the basis of our analysis. This measure is used extensively within transportation planning to look at distance traveled in terms of total distance per person trip.
We identified both a typical per-household VMT as well as the typical mode-share breakdown for suburban and urban settings similar to the two communities identified. We validated this against existing VMT information and modeshare breakdown for other similar urban environments.
ESTIMATING EMISSIONS BY DIFFERENT VEHICLE TYPES
We used data from Replica, an industry-leading database33 , to break down private vehicles into cars, vans and trucks. This helped to more accurately estimate emissions, since different types of vehicles emit different amounts of CO 2 . We then divided vehicle types by fuel type using data from the US Department of Energy34. This enabled our team to identify the percentage of gas, diesel, plug-in hybrid, hybrid or battery electric vehicle (EV) vehicles for each class of vehicle.
From there, we could calculate the emissions per vehicle using emissions factors from the California Air Pollution Control Officers Association (CAPCOA)35. We also adjusted our results based on variations in transit usage seen between suburban and urban settings thanks to data from US Federal Highway Administration (FHWA)36
Using emission factors from CAPCOA, we calculated carbon emissions per vehicle. We also considered transit usage, factoring in bus occupancy differences between suburban and urban settings. This helped to account for the varying transit efficiencies across different urban environments. To estimate the overall transportation emissions over the building’s lifecycle, we incorporated goals set by states such as New York and California for transitioning to zero-emission vehicles (ZEV).
Who needs to know?
Key Audiences Our Four Core Questions
We believe this study is especially relevant for organizations that are involved in communitylevel planning — such as universities, Fortune 500 companies, and major property development firms — and that control assets from initial planning all the way to decommissioning. These organizations will have to factor in these types of carbon emissions into their ESG reporting in some way, and with no fracturing of emissions across the value chain.
This study will also help urban planners and municipal policymakers identify where their efforts can have the greatest impact.
Finally, it will help banks and other financiers consider how to best limit their financed emissions37 .
Considering the built environment as a whole, which of the two ends of the urban development spectrum — tall or sprawl — leads to lower impacts on the climate?
1 3 2 1 4 3
Do the bulk of whole life carbon emissions come from energy, refrigerant leaks, building materials, or daily transportation?
Do most emissions occur upfront, over time, or at the end of an asset’s life?
What design decisions have the potential to deliver the greatest value to an asset owner focused on decarbonization?
Our Five Primary Assumptions
Two familiar forms of residential built environments, both housing 600 people.
Assessing impacts on the climate from 2024 to 2084 (a 60-year lifespan).
After the first HVAC systems reach their end of life in the two models, future HVAC system refrigerants are assumed to have significantly lower Global Warming Potentials, in order to align with the 2016 Kigali Amendment to the Montreal Protocol.
Buildings in both urban and suburban environments were operationally decarbonized, aligning with the World Green Building Council’s call for all new buildings to be net zero operational carbon by 203038.
In line with goals made by leading countries and states, from 2035 onwards all vehicles were assumed to be zeroemissions vehicles 39 (i.e. battery electric vehicles).
KEY RESULTS
Key Results
(data reported in kgC0₂ equiv.)
Which built environment is lower impact?
The Tall, Urban Tower is the lower impact form of built environment - but not overwhelmingly.
These two sets of results barely appear different when considering impacts on a per-square-meter basis. Where the two scenarios appear more distinct is when they are judged on the basis of “carbon per capita” or “carbon per household”.
This calls into question the suitability of relying on per-square-meter targets for residential built environments.
It’s worth noting that developers of Suburban communities who are committed to net zero emissions can create neighborhoods that challenge this ranking (by implementing elements of our Eight Point Plan).
TALL, URBAN TOWER SUBURBAN COMMUNITY
Key Results
(data reported in kgC0₂ equiv.)
URBAN TOWER
Where do the bulk of carbon emissions come from?
Up to 2030, our research found that nearly half of carbon emissions (39-49%) will come from the production of the materials needed for building structures, enclosures, and MEP41. However, by 2084, user transportation emissions will dominate the overall results, outpacing everything else within as little as 10 years.
A significant number of daily trips are completed by bike or foot - but as zero emissions modes of travel, there are no carbon emissions associated with them.
SUBURBAN COMMUNITY
Key Results
(data reported in kgC0₂ equiv.)
When do most emissions occur?
SUBURBAN TOWER
TALL, URBAN TOWER SUBURBAN COMMUNITY
Our modelling reveals that even in an operationally decarbonized building, twothirds of total carbon emissions for our built environments will be accumulated over their operational life - due to the ongoing impacts from primarily user transportation, and occasional impacts from replacing finishes, MEP systems, or furniture. Therefore, there is ongoing value in procuring low carbon materials and investing in decarbonized transportation options for all buildings, not just new ones.
Key Results
(data reported in kgC0₂ equiv.)
Which Design Solutions have the greatest potential?
If, by 2030, most embodied carbon emissions will come from structural and enclosure materials, then short-term action plans must mitigate those emissions in order to buy as much time as possible before passing the 1.5C threshold. These actions include the adaptive reuse of existing buildings, reusing individual materials, utilizing low-carbon concrete mixes or steel, or designing with mass timber.
By 2084, user transportation carbon emissions will dominate results. Planners and designers have to incentivize zero emissions modes of transport and encourage the usage of shared transportation. We expect it would include promoting walkability, transit connectivity, and bicycle-friendly design, as well as carsharing and EV charging42
Vancouver’s Canada Post Office building, now known as “The Post,” had its heritage facade retained and adaptively reused the 1960’s steel-frame structure to cut thousands of tonnes of carbon that would otherwise have been emitted in construction. Introba’s team played a key role in the project, providing mechanical, sustainability, and fire protection consulting services.
Rico Marques
Immediate Next Steps: An Eight-Point Plan
1 Eliminate the overbuilding of car-centric infrastructure as soon as possible.
This change would have a huge impact on both short- and long-term carbon emissions. Cities should strike down minimum parking requirements and developers should “unbundle” parking from home sales and rentals to limit market distortion. With the true costs made clear to both development teams and individuals, people are likely to reconsider whether their primary mode of transportation should be a private vehicle. It would also avoid releasing the significant amounts of embodied carbon needed for the construction of parking areas, which is even more significant when located underground.
2 Integrate attractive, quality, sustainable transportation choices into the next generation of urban and suburban communities.
This is a huge opportunity for architects, developers, and urban planners. Vehicle electrification is no longer sufficient for communities to reach their emissions reduction goals. Modal change is the highest priority in delivering emissions reduction in transportation. Cities should improve public transportation for the vast majority providing residents with easy access to multiple ways of getting where they need to go within a reasonable timeframe. A combination of transportation strategies to electrify vehicles and to shift more people into shared modes of transportation will have the greatest long-term impact on addressing carbon emissions.
3 Analyze carbon emissions at the scale of the built environment.
This must be a high priority for any organization that deploys capital for urban development. This is true for both primary developers or for those in finance when tracking Scope 3 emissions for ESG reporting. While not as questionable an investment as oil and gas, project financiers should be aware when they are funding something with higher emissions than others, and therefore to know when and how to push architects and engineers to incorporate sustainable transportation measures to decrease the financed emissions of their portfolios.
4 Push for building codes that explicitly set whole-life carbon limits.
A vital item for the agenda for federal, provincial, or state governments. Ambition and action of this scale should not be the burden of cities alone. By adopting consumption-based carbon emissions accounting practices that resemble the Danish model43 , governments can set builtenvironment-scale whole-life carbon targets for new neighborhood masterplan projects.
43 For details, see here: https://www.introba.com/news/lessons-denmark-sustainable-design-and-whole-life-carbon-emissions
Immediate Next Steps: An Eight-Point Plan
5 Provide stable and sufficient funding for key NGOs.
Funding for Non-government organizations (“NGOs”) that work tirelessly to reduce whole life carbon emissions should be on all government and industry to-do lists. These organizations include the Athena Sustainable Materials Institute 44, the Carbon Leadership Forum45 (CLF) and its local hubs 46 , the Low Energy Transformation Initiative 47 (LETI), and Building Transparency48
6 Add transportation impacts to zero carbon certification standards worldwide.
This would ensure long-term credibility and reporting rigor. This is not entirely novel; the LEED Zero Carbon program - while imperfect as it omits embodied impacts - does currently include Transportation impacts in it’s Carbon Balance. Design teams have been considering Location and Transportation impacts as a part of holistic sustainability strategies for buildings for nearly twenty years - as we focus more on carbon, let us not stop now.
44 https://www.athenasmi.org/
45 https://carbonleadershipforum.org/
46 https://clfbritishcolumbia.com https://www.clfboston.com and many more!
47 https://www.leti.uk/
48 https://www.buildingtransparency.org/
7 Publish studies summarizing the whole life carbon of infrastructure projects with clear reference values.
CIBSE TM65.1 in the UK is an excellent example of how effective this can be and how it would allow more people to adopt this approach for their projects. Carbon accounting is a widespread practice for structures and enclosures in leading markets such as California, the UK, and parts of Canada. The industry is also actively pushing to achieve zero carbon across all elements of a building in the not-too-distant future (SE 205049, MEP 204050, and Architecture 203051). New case studies of the estimated carbon emissions of sidewalks, roads, sewers, and water works would provide a place to begin to tackle infrastructure emissions on a per-project basis.
8 Encourage leading scientists and economists to share guidance on what discount rate should be used to calculate the net present value (NPV) of one kilogram of carbon dioxide.
This move would support passionate teams with limited budgets in striking the optimum balance between short - and long-term carbon emissions mitigation strategies.
49 A movement led by Structural Engineering (SE) firms to work toward net zero embodied carbon structural systems by 2050 https://se2050.org/
50 A movement led by Mechanical, Electrical, and Plumbing (MEP) engineering firms to achieve net zero embodied carbon building systems by 2040 (of which Introba was a founding signatory) - https://www.mep2040.org/
51 The first of the industry challenges - issued back in 2005 - it is a movement led by Architects to achieve net zero operational carbon buildings by 2030https://www.architecture2030.org/
End Notes
Known Omissions
Some key things were known to be unknown at this time, and they have been knowingly omitted from this study as a result. Those were:
Biogenic sequestration of carbon in wood and other biobased products (that are especially common in suburban settings and in certain finishes and furniture products) has been left out intentionally as it is a very nuanced topic.
If it was included, it would likely improve the results for the Suburban case, but only if the wood could be guaranteed to come from sustainable forests (which is itself complicated), and not be sent to landfill at the end of life (which is especially common in residential settings).
Construction Impacts (LCA Module A5) are likely underrepresented.
This is a space of active development, and market leaders such as Microsoft 52 are doing great work to improve the state of the practice. By some numbers, A5 impacts are underreported by a factor of about fourfold. This would likely worsen the results for both cases equally.
Not all infrastructure impacts are sufficiently understood at this time.
We did not include sewers, power lines, street lighting, potable water, and telecom system elements in this study.
Structure and Enclosure Per Introba-produced LCA model for a real project
Interiors Per square-meter intensity values from 6 Camden Mews study by Max Fordham
MEP Systems
Per CIBSE TM65.1 Intensity for a Central Air Source Heat Pump-based system in a 100-unit Development (86 kgCO2e/m2) and per internally-conducted studies for non-HVAC MEP impacts (168 kgCO₂e/m2)
Per EMBARC Weighted Average Intensity for Single Detached based on heated floor area for LCA Modules A1-A3, scaled across the lifecycle using the factors within the City of Vancouver Embodied Carbon Guidelines V1.0
Per square-meter intensity values from 6 Camden Mews study by Max Fordham
Per CIBSE TM65.1 Intensity for a VRF-based system in a three-bedroom house (74 kgCO2e/m²) and per internally-conducted studies for non-HVAC MEP impacts (200 kgCO₂e/m2)
Refrigerants
Custom calculations for two heat pumps with a total capacity of 325 tonnes specified for a real building’s HVAC system, using GWP values from IPCC AR4 & leakage rate assumptions from LEED V4’s “Enhanced Refrigerants” credit
Operational Emissions
Using Annual Greenhouse Gas Intensity (GHGI) limit of 1.8 kgCO2e/m² for complex buildings per the Province of British Columbia’s Zero Carbon Step Code, specifically Emissions Level 4 (EL-4)
Civil Infrastructure No infrastructure impacts assigned due to infill setting
Landscaping
Custom calculations, using per-square-meter values for live plantings from the Climate Positive Design Pathfinder Tool , assuming the property is planted with 40% shrubs and 60% pedestrian hardscape.
Custom calculations for 150 homes each with a five-tonne heat pump, using GWP values from IPCC AR4 & leakage rate assumptions from LEED V4’s “Enhanced Refrigerants” credit
Using Annual GHGI of 1.5 kgCO2e/m2 for low-rise residential buildings per the Province of British Columbia’s Zero Carbon Step Code, specifically EL-4
Per Introba-produced LCA model
Custom calculations, using per-square-meter values for live plantings from the Climate Positive Design Pathfinder Tool, assuming each property includes 20% shrubs, 60% lawn, 5% pedestrian hardscape, and 15% driveway.
Excavation
Land Use, Land Use Change, and Forestry (LULUCF)
Per-cubic-meter excavation emissions value from Oneclick LCA multiplied by below-grade volume
Per hectare values from Canadian 2023 UNFCCC Submission for conversion of ~17,000 m²
Custom VMT Calculations using data for an Urban setting from:
• UC Davis for the California Air Resources Board
User Transportation
• US Federal Highway Administration
• US Department of Energy
• California Air Pollution Control Officers Association
No excavation impacts assigned
Per hectare values from Canadian 2023 UNFCCC Submission for conversion of ~72,400 m2
Custom VMT Calculations using data for Suburban, Single-Family settings from:
• UC Davis for the California Air Resources Board
• US Federal Highway Administration
• US Department of Energy
• California Air Pollution Control Officers Association
